A build sysytem

I want to make my own build system, and so wondered if anyone had any tips or know about a smaller, simpler build system I could look at.

My idea at the moment is to check change date of the output and input and then the command.
So something like :

binary <> sourcefile.ext <> compiler -o binary

Heed it would mean that it's incremental and wouldn't be hard to implement.

But do anyone have any ideas, or a better way to do it?

If anything at all, please just tell.

I now have a working prototype of the build system.

vc <> vc.ml te.ml <> ocamlfind ocamlopt -ccopt -s -compact -linkpkg te.ml -package unix vc.ml -o vc

FORMAT:
     [1] binary < > [2] source files < > [3] cli command
     [1]- file to check modification date of
     [2]- source files to check the modification date against
        - If source files modified after binary run the cmd
     [3]- The command to run

run< > cmd
    - run< > will run the cmd no matter what

This is now used in the project itself.
Can be seen at https://git.catkin.dev/trondelag/misc/src/branch/rein